Apparatus for manufacturing hydro dynamic bearing device method

ABSTRACT

An apparatus for manufacturing a hydro dynamic bearing device is provided for the finishing treatment of lubricating oil after lubricating the hydro dynamic bearing device. The hydro dynamic bearing is constructed of an axial member housed in a housing, a radial bearing part for supporting the axial member in a non-contact manner in a radial direction by a hydro dynamic pressure action of the lubricating oil generated in a radial bearing clearance, and a sealing part arranged in an opening part of the housing, and the apparatus has a laser for measuring an oil-level height of the lubricating oil in the housing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and an apparatus formanufacturing a hydro dynamic bearing device. In particular, the presentinvention relates to a method and an apparatus for manufacturing a hydrodynamic bearing device to be used in a spindle motor equipped in aninformation technology device such as a magnetic disk device (e.g., HDDor FDD), an optical disk device (e.g., CD-ROM, CD-R/RW, or DVD-ROM/RAM),and an optical magnetic disk device (e.g., MD or MO), a scanner motorequipped in a copying machine, a laser printer (LBP), a barcode reader,or the like, or a small-sized motor equipped in an electrical equipmentsuch as an axial fan.

2. Description of the Related Art

As is generally known in the art, each kind of the motors listed abovehave been promoted to be provided at lower cost, driven at higher speedand more quiet, and so on in addition to attain a high rotationalaccuracy. As one of factors that define these required performances, abearing supporting spindle of the motor has been increasingly valued. Inrecent years, therefore, as such a kind of the bearing, the use of ahydro dynamic bearing having excellent characteristics that serve arequest for the above performance has been studied, and such a hydrodynamic bearing has been developed in a quest to put it to practicaluse.

For instance, a hydro dynamic bearing device to be built in a spindlemotor of a disk device such as a hard disk drive (HDD) comprises aradial bearing part for rotatably retaining an axial member in anon-contacting manner in the radial direction and a thrust bearing partrotatably retaining the axial member in a non-contacting manner in thethrust direction. As a bearing part of each of them, a hydro dynamicbearing device having a groove (a hydro dynamic pressure generatinggroove) for the generation of hydro dynamic pressure on its bearingsurface is used.

In this case, the hydro dynamic pressure generating groove of the radialbearing part is formed in the inner peripheral surface of the bearingmember or the housing, or formed in the outer peripheral surface of theaxial member. On the other hand, in the case of using an axial memberhaving a flange part, the hydro dynamic pressure generating groove ofthe thrust bearing part is formed in each of the opposite end faces ofthe flange part or the surface (e.g., the end face of the bearing memberor the bottom surface of the housing) facing to such an end face.

In addition, when an axial member having no flange part is used, theremay be adapted a structure that retains the end face of the axial memberby a thrust plate attached on the bottom surface of the housing withoutforming a hydro dynamic pressure generating groove in the bearingsurface as a thrust bearing part.

In each of these hydro dynamic bearing devices, furthermore, the axialmember is projected outward from the opening part of the housing. Forsealing the lubricating oil filled in the housing, a sealing part thatcovers the periphery of the axial member through a small clearance isprovided on the opening part of the housing.

In the final stage of manufacturing such a kind of the hydro dynamicbearing device, a hydro dynamic bearing device is assembled withoutlubrication and is then dipped in lubricating oil in a vacuum tank,followed by opening the chamber to atmospheric pressure to fill theinner space of the housing with the lubricating oil.

Subsequently, the hydro dynamic bearing device is removed from thevacuum tank after filling with the lubricating oil. In this case,however, a large amount of the lubricating oil adhere to various partsof the removed hydro dynamic bearing device, for example to the outerperipheral surface and the outer bottom surface of the housing, theouter end face of the sealing part, and the outer end face of the axialmember.

Then, the lubricating oil adhering to each of these parts is wiped offat a subsequent step. Conventionally, the wiping has been performedusing a sheet or film formed of a resin material based on polyethylene,polyvinyl chloride, polyvinylidene chloride, or the like, specificallysuch as Saran Wrap (trade name) manufactured by Asahi Kasei Corporation.

However, when the lubricating oil is wiped off using the resin film orthe like as described above, the wiping is a complicated and very hardwork that takes much time to complete, while becoming too burdensome forthe worker. Consequently, there is a possibility of decreasing theworking efficiency. In this method, furthermore, there is a tendencythat it becomes difficult to properly wipe the lubricating oil off fromeach of the above parts.

That is, the housing of this kind of the hydro dynamic bearing devicetypically comprises a lateral part having an outer peripheral surfaceand a bottom part having an outer bottom surface, which are separatelyprovided and fixed together with caulking or the like. Therefore, anuneven spot or a step is found in the joining area between thesecomponents. Therefore, when the lubricating oil adhering to the housingis wiped off using the resin film or the like as described above, theuneven spot or the like stands in the way of wiping the lubricating oilto prevent a smooth wiping-off operation. In addition, there is apossibility of remaining the lubricating oil still in a recessed part.As a result, it is concerned about the quality of the product which maydecrease.

In addition, on the opening part side of the housing, the axial memberis protruded outward by passing through a through hole formed on thecenter of the sealing part, resulting in that the axial member stands inthe way of wiping off the lubricating oil around the axial member usingthe resin film or the like as described above. Consequently, there is apossibility that it becomes difficult to wipe off the lubricating oil onthe outer end face of the sealing part and the outer end face of theaxial member, and it is difficult to prevent the lubricating oil beingremained in place.

Meanwhile, the wiped hydro dynamic bearing device (or one beingsubjected to rough wiping) is heated up to an upper limit temperature ofthe operation to thermally expand the lubricating oil filled in theinternal space of the housing, removing an excess amount of thelubricating oil therefrom.

This kind of the treatment brings down the oil level of the lubricatingoil at room temperature as much as sufficient to keep it an appropriatelevel to prevent the lubricating oil from being leaked due to thethermal expansion of the oil when the hydro dynamic bearing drive isoperated at an upper limit temperature of the operation. In addition, anexcess amount of the lubricating oil being overflowed at this time(i.e., a small amount of the lubricating oil) is also subjected to thewiping-off treatment.

Under present circumstances, the oil level of the lubricating oil in thehydro dynamic bearing device is adjusted such that an increased part ofthe oil level concurrently with the thermal expansion is absorbed withan oil-absorbing member such as a cotton swab at the time of heating thelubricating oil after the lubricating oil has been filled in the innerspace of the housing.

However, the conventional adjustment of oil level is performed usingsuch a naturally-occurring absorbing action, i.e., a capillary phenomenaor the like, and in this case, the absorbing performance and theabsorbing function of the above action depend on the characteristics ofan absorber such as a cotton material, while it is also influenced bythe degree of practiced experiences of a worker. Therefore, themanagement of the oil-level height of the lubricating oil in the housingmay be difficult since variations in absorbing volume may occur.

When the above variations cause a shortage of the lubricating oil in thehousing, several troubles occur, for example insufficient lubrication ofthe bearing device. Consequently, the hydro dynamic bearing device maydeteriorate earlier than expected. In addition, when the amount of thelubricating oil in the housing is excessive, there is a possibility ofcausing a leakage of the lubricating oil to the outside when the hydrodynamic bearing device is operated at an upper-limit temperature of theoperation.

BRIEF SUMMARY OF THE INVENTION

The present invention has been completed in consideration of the abovecircumstances. It is a technical object of the present invention toprovide a method and an apparatus for manufacturing a hydro dynamicbearing device that allows a worker to properly and efficiently performa finishing treatment for dealing with the lubricating oil afterlubricating the hydro dynamic bearing device, more specifically toproperly and efficiently wipe the lubricating oil adhering to theoutside area of the housing and adjust an oil level height of thelubricating oil being filled in the inside of the housing.

In order to resolve the above technical problem, a first aspect of thepresent invention is a method (hereinafter also referred to as a firstmethod) for manufacturing a hydro dynamic bearing device including ahousing, an axial member housed in the housing, a radial bearing partfor supporting the axial member in a non-contact manner in a radialdirection by a hydro dynamic pressure action of a lubricating oilgenerated in a radial bearing clearance, and a sealing part formed onone end part of the housing. The method includes the step of wiping offthe lubricating oil adhering to an outer bottom surface and an outerperipheral surface of the housing by blowing a gas at least on thesesurfaces after applying the lubricating oil to the housing;

Here, although the “gas” is preferably the atmospheric air, it may beinert gas such as nitrogen or argon, or a mixture thereof.

According to such a configuration of the first method, the lubricatingoil adhering at least to the outer bottom surface (the bottom surfaceexposed to the outside) and the outer peripheral surface of the housingis blown off or streamed with blowing to wipe off the undesiredlubricating oil on these surfaces. Therefore, there is no need ofdifficult and complicated work such as the conventional work of wipingoff the lubricating oil using a resin film or the like, resulting in anextensive improvement of the working efficiency. In addition, thelubricating oil, which is being in a state of easily remaining in arecessed or stepped part of the housing, can be easily wiped off by thegas even in the case of: having a recessed part or a stepped part in thejoining area between a lateral part having an outer peripheral surfaceand a bottom part having an outer bottom surface, which are separatelyprovided and then fixed together with caulking or the like to constructthe housing; or having a recessed part or a stepped part in the otherpart of the housing. Consequently, the lubricating oil can be properlyremoved at least from the outer bottom surface and the outer peripheralsurface of the housing, so that a high-quality hydro dynamic bearingdevice can be obtained.

In order to resolve the above technical problem, a second aspect of thepresent invention is an apparatus (hereinafter also referred to as afirst apparatus) for manufacturing a hydro dynamic bearing deviceincluding a housing, an axial member housed in the housing, a radialbearing part for supporting the axial member in a non-contact manner ina radial direction by a hydro dynamic pressure action of a lubricatingoil generated in a radial bearing clearance, and a sealing part formedon one end part of the housing. The apparatus includes wiping-off meansfor wiping off the lubricating oil adhering at least to an outer bottomsurface and an outer peripheral surface of the housing after applyingthe lubricating oil to the housing, wherein the wiping-off means isconstructed of gas-blowing means for blowing a gas on each of thesurfaces.

According to such a configuration of the first apparatus, thelubricating oil adhering at least to the outer bottom surface (thebottom surface exposed to the outside) and the outer peripheral surfaceof the housing is blown off or streamed with blowing to wipe off theundesired lubricating oil on these surfaces. Therefore, the same effectsas that of the first method of the present invention can be attained.

In this case, preferably, a gas-flowing passage may be formed such thatthe gas from the single gas-blowing means flows along the outer bottomsurface and the outer peripheral surface of the housing. Consequently,only by providing single gas-blowing means, the lubricating oil adheringto the above both surfaces of the housing can be wiped off all at onceby the gas even though the outer bottom surface and the outer peripheralsurface of the housing are arranged perpendicular to or almostperpendicular to each other. Therefore, the configuration of theapparatus described above can reduce the number of structural parts ofthe device to be used for the wiping-off operation, can achieve theminiaturization of the device, and also reduce the cost of the device,while contributing a reduction in the manufacturing costs.

In addition, it is preferable that the hydro dynamic bearing device isheld such that the sealing part is located downward, and an areaextending from the outer end face of the sealing part to the axialmember is shielded from the gas-flowing passage. Consequently, thelubricating oil can be effectively wiped off by, for example, blowingthe gas downward to stream the lubricating oil under its own weight fromthe outer bottom surface to the outer peripheral surface of the housing.In addition, the area extending from the outer end face of the sealingpart (the end face of the sealing part exposed to the outside) to theaxial member is shielded from the gas-flowing passage. Therefore, asdescribed above, even though the lubricating oil flows downward alongthe outer peripheral surface of the housing, there is no possibility ofcausing trouble in which the lubricating oil flows and adheres to theouter end face of the sealing part or to the axial member, or thelubricating oil flows into a sealing space between the sealing part andthe axial member.

In order to resolve the above technical problem, a third aspect of thepresent invention is a method (hereinafter also referred to as a secondmethod) for manufacturing a hydro dynamic bearing device including ahousing, an axial member housed in the housing, a radial bearing partfor supporting the axial member in a non-contact manner in a radialdirection by a hydro dynamic pressure action of a lubricating oilgenerated in a radial bearing clearance, and a sealing part formed onone end part of the housing. The method includes the step of wiping offthe lubricating oil adhering to an outer end face of the sealing partand an outer end face of the axial member by acting a negative-pressuresuction force by suction means at least on the outer end faces afterapplying the lubricating oil to the housing.

According to the configuration of the second method, the lubricating oiladhering at least to the outer end face of the sealing part and theouter end face of the axial member (the end face of the axial memberexposed to the out side) is sucked by the suction means under a negativepressure to wipe off the undesired lubricating oil on these outer endfaces. There is no need of difficult and complicated work of wiping offthe lubricating oil using a resin film or the like. Thus, it becomespossible to improve the working efficiency to a large extent.Furthermore, even though the axial member protrudes from the sealingpart outside, the procedure based on negative-pressure suctionsubstantially prevent the axial member from standing in the way ofwiping off the lubricating oil. Therefore, the wiping can be performedappropriately without improperly remaining the undesired lubricating oilon a part where it is difficult to wipe the lubricating oil due to thepresence of the axial member.

In order to resolve the above problem, a fourth aspect of the presentinvention is an apparatus (hereinafter also referred to as a secondapparatus) for manufacturing a hydro dynamic bearing device including ahousing, an axial member housed in the housing, a radial bearing partfor supporting the axial member in a non-contact manner in a radialdirection by a hydro dynamic pressure action of a lubricating oilgenerated in a radial bearing clearance, and a sealing part formed onone end part of the housing. The apparatus includes wiping-off means forwiping off the lubricating oil adhering at least to an outer end face ofthe sealing part and an outer end face of the axial member afterapplying the lubricating oil to the housing, wherein the wiping-offmeans is constructed of suction means for making a negative-pressuresuction force act on these outer end faces.

According to the configuration of the second apparatus as describedabove, the lubricating oil adhering at least to the outer end face ofthe sealing part and the outer end face of the axial member (the endface of the axial member exposed to the outside) is sucked by suctionmeans under a negative pressure to wipe off the undesired lubricatingoil on these outer end faces. Therefore, the same effects as those ofthe second method of the present invention can be obtained.

In this case, preferably, the suction means may include two suctionnozzles, one used for the outer end face of the sealing part and theother used for the outer end face of the axial member. Consequently, theamount of the lubricating oil being sucked can be stably adjusted andalso easily managed by managing the nozzle diameter, nozzle-tipposition, and sucking force of each suction nozzle. Furthermore, thenozzle tip can be easily arranged on a part where it is difficult towipe off the lubricating oil due to the presence of the axial member.Therefore, the wiping-off operation can be more appropriately performed.

Furthermore, preferably, the lubricating oil may be sucked and wiped offby the suction means while rotating the hydro dynamic bearing deviceabout the axial center by the rotation jig. Consequently, the entireperimeter of each of the outer end face of the sealing part and theouter end face of the axial member can be subjected to the wiping-offaction only by holding the suction means on a fixed position or a simplereciprocating motion such as a swing motion of the suction means,contributing a simplification of the mechanism for moving the suctionmeans and also contributing a simplification of the device required forthe wiping-off operation and a cost reduction in providing such adevice.

Furthermore, to resolve the above technical problem, the followingmethod may be applied instead of the methods described above.

That is, after applying the lubricating oil to the housing, a rotationalforce about the axial center is given to the hydro dynamic bearingdevice, and at the same time the oil-absorbing member is made contactwith each of the outer end face of the sealing part and the outer endface of the axial member to wipe off the lubricating oil adhering tothese outer end faces.

In this case, it may be constructed such that the hydro dynamic bearingdevice is intermittently rotated about the axial center to make theabove oil-absorbing member contact with each of the above outer endfaces at the time of suspending the rotary motion.

Alternatively, it may be constructed such that a continuous rotarymotion about the axial center is given to the above hydro dynamicbearing device while stopping the rotation of the hydro dynamic bearingdevice by an abutting force of the oil-absorbing member against each ofthe above outer end faces.

In order to resolve the above technical problem, a fifth aspect of thepresent invention is a method (hereinafter also referred to as a thirdmethod) for manufacturing a hydro dynamic bearing device including ahousing, an axial member housed in the housing, a radial bearing partfor supporting the axial member in a non-contact manner in a radialdirection by a hydro dynamic pressure action of a lubricating oilgenerated in a radial bearing clearance, and a sealing part formed onone end part of the housing. The method includes the step of: suckingthe lubricating oil from a sealing space of the sealing part or avicinity thereof by suction means for generating a negative-pressuresuction force to adjust an oil-level height of the lubricating oil inthe housing.

According to such a configuration of the third method, the amount of thelubricating oil after lubricating the hydro dynamic bearing device isadjusted by the suction means that generates a suction force under anegative pressure. Therefore, the control of the suction force and alsothe control of the suction oil amount can be performed stably, comparedwith the conventional method that uses a naturally-absorbing action witha cotton swab or the like. Consequently, it becomes possible toprecisely and easily manage the oil-level height and amount of thelubricating oil, so that problems of early deterioration of the bearingdevice due to a leakage of the lubricating oil to the outside and poorlubrication at the time of driving the hydro dynamic bearing device atan upper limit temperature of the operation can be effectively avoided.

The oil-level height may be measured by means of a laser after suckingthe lubricating oil at the time of adjusting the amount of oil asdescribed above, Consequently, a high-quality hydro dynamic bearingdevice can be provided in the market since the selection between thegood product and the defective product can be performed by confirmingwhether the suction oil amount of the lubricating oil by the suctionmeans is correct using a laser.

In order to resolve the above technical problem, a sixth aspect of thepresent invention is to provide an apparatus (hereinafter also referredto as a third apparatus) for manufacturing a hydro dynamic bearingdevice including a housing, an axial member housed in the housing, aradial bearing part for supporting the axial member in a non-contactmanner in a radial direction by a hydro dynamic pressure action of alubricating oil generated in a radial bearing clearance, and a sealingpart formed on one end part of the housing. The apparatus includessuction means for sucking the lubricating oil from a sealing space ofthe sealing part or a vicinity thereof under a negative pressure toadjust an oil-level height of the lubricating oil in the housing.

According to such a configuration of the third method, the adjustment ofthe amount of the lubricating oil after lubricating the hydro dynamicbearing device is performed by the suction means that sucks thelubricating oil under a negative pressure. Therefore, just as with themanufacturing method described above, it becomes possible to preciselyand easily manage the oil-level height and the amount of the lubricatingoil. Problems of early deterioration of the bearing device due to aleakage of the lubricating oil to the outside and badness of lubricationat the time of driving the hydro dynamic bearing device at an upperlimit temperature of the operation can be effectively avoided.

In this case, preferably, the suction means may include a suctionnozzle. The nozzle diameter, nozzle-tip position, suction force, andsuction time of the suction nozzle can be managed to adjust theoil-level height in a stable manner and to manage such an adjustment ina simple manner. Therefore, the advantages of the manufacturingapparatus described above can be attained more easily.

Furthermore, the suction means may be capable of being close to or beingaway from the sealing space in a relative manner. Consequently, itbecomes possible to place the suction means (the suction portionthereof) on the sealing space or the vicinity thereof when the amount oflubricating oil in the housing should be adjusted. Also it is possibleto relatively displace the suction means away from the sealing space toits retracting position when the adjustment of the amount of oil iscompleted. Consequently, for example, it becomes possible to make thefabrication procedure automatic and also to speedup the procedure whenthe hydro dynamic bearing device is produced on an assembly line.

Furthermore, preferably, a rotation jig for rotating the hydro dynamicbearing device about an axial center may be equipped in the apparatusfor manufacturing the hydro dynamic bearing device. According to such aconfiguration of the apparatus, it becomes possible to suck and wipe offthe lubricating oil by the suction means while rotating the hydrodynamic bearing device about the axial center by the rotation jig. Asthe suction means is allowed to suck the lubricating oil directly overthe entire perimeter of the sealing space, the amount of the lubricatingoil can be adjusted more precisely and uniformly.

In the manufacturing apparatus having the structural componentsdescribed above, it is preferable to equip a laser for measuring theoil-level height of the lubricating oil after sucking the oil. In thiscase, furthermore, similarly to the manufacturing method describedabove, a high-quality hydro dynamic bearing device can be provided inthe market since the selection between the good product and thedefective product can be performed by confirming whether the suction oilamount of the lubricating oil by the suction means is correct using alaser.

In order to resolve the above-mentioned technical problem, a seventhaspect of the present invention is to provide a method (hereinafter alsoreferred to as a fourth method) for manufacturing a hydro dynamicbearing device including a housing, an axial member housed in thehousing, a radial bearing part for supporting the axial member in anon-contact manner in a radial direction by a hydro dynamic pressureaction of a lubricating oil generated in a radial bearing clearance, anda sealing part formed on one end part of the housing. The methodincludes the step of measuring an oil-level height of the lubricatingoil in the housing by a laser.

According to such a configuration of the fourth method, afterlubricating the hydro dynamic bearing device during the manufacturingprocess, whether the amount of the lubricating oil filled in the housingis proper or not, that is, whether the oil amount is properly adjustedor not can be confirmed by means of a laser (laser beam). Thereby, it ispossible to detect whether the oil amount is insufficient or excess withaccuracy. Further, it contributes to automation of the oil-level heightdetection.

As a concrete example, a laser displacement meter as laser displacementdetermining means is arranged at a position a predetermined distanceaway from the sealing part of the housing. A distance from a standardposition of the laser displacement meter to the sealing part and adistance from the standard position of the laser displacement meter tothe oil-level height are detected. Based on a comparison result betweentwo detected distances, the oil-level height of the lubricating oil inthe housing is detected. Then, based on the detected oil-level height,whether the amount of the lubricating oil in the housing is proper ornot is judged.

In this case, it is preferred to detect the two distances in directionsparallel to each other. Namely, the irradiation direction of the laserbeams is parallel to another. In order to do so, the laser displacementmeter is preferably configured to detect the two distances at twopositions by moving the meter in a direction perpendicular to the axialcenter of the hydro dynamic bearing device. Alternatively, two laserdisplacement meters are arranged at two locations along the directionperpendicular to the axial center of the hydro dynamic bearing device.In a preferred embodiment, the two distances are detected along thedirection parallel to the axial center of the hydro dynamic bearingdevice. In other words, the irradiation direction of the laser beam isparallel to the axial center of the hydro dynamic bearing device. Atleast one position in the circumferential direction is enough for themeter to detect the two distances, although two or more positions, forexample, two positions separated by 180 degrees are preferred.

In order to resolve the above-mentioned technical problem, an eighthaspect of the present invention is to provide an apparatus (hereinafteralso referred as a fourth apparatus) for manufacturing a hydro dynamicbearing device including a housing, an axial member housed in thehousing, a radial bearing part for supporting the axial member in anon-contact manner in a radial direction by a hydro dynamic pressureaction of a lubricating oil generated in a radial bearing clearance, anda sealing part formed on one end part of the housing. The apparatusincludes a laser for measuring an oil-level height of the lubricatingoil in the housing.

According to such a configuration of the present invention, whether theamount of the lubricating oil filled in the housing is proper or not canbe confirmed by means of a laser (laser beam). Thereby, it is possibleto detect whether the oil amount is insufficient or excess withaccuracy. Further, it contributes to automation of the apparatus (inpreferred embodiment fully automated apparatus). In this case, also thelaser displacement meter as laser displacement means is arranged toperform the same operation as in the previous embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic front view showing an apparatus for wiping offlubricating oil for use in a first method for manufacturing a hydrodynamic bearing device in accordance with one of embodiments of thepresent invention.

FIG. 2A is a vertical cross sectional front view showing the innerstructure of the hydro dynamic bearing device in accordance with one ofthe embodiments of the present invention, and FIG. 2B is an enlargedvertical cross sectional front view showing a part marked with theletter A in FIG. 2A, respectively.

FIG. 3 is a schematic front view showing the configuration of awiping-off apparatus for use in a second method for manufacturing ahydro dynamic bearing device in accordance with one of the embodimentsof the present invention.

FIG. 4 is a schematic front view showing another example of theconfiguration of a wiping-off apparatus for use in the second method formanufacturing a hydro dynamic bearing device in accordance with one ofthe embodiments of the present invention.

FIG. 5 is a schematic front view showing the configuration of an oillevel controller for use in a third method for manufacturing a hydrodynamic bearing device in accordance with one of the embodiments of thepresent invention.

FIG. 6A is a vertical cross-sectional front view showing theconfiguration of the hydro dynamic bearing device where the third methodfor manufacturing a hydro dynamic bearing device in accordance with theinvention is performed, and FIG. 6B is a partially enlarged verticalcross-sectional front view showing a part marked with the letter A inFIG. 6A, respectively.

FIG. 7 is a partially enlarged vertical cross-sectional front viewshowing the hydro dynamic bearing device where a fourth method formanufacturing a hydro dynamic bearing device in accordance with one ofthe embodiments of the present invention is performed.

FIG. 8 is a schematic front view showing the oil-level height detectorfor use in the fourth method for manufacturing the hydro dynamic bearingdevice according to one embodiment of the present invention.

FIG. 9 is a schematic vertical cross-sectional front view showing astate in which the hydro dynamic bearing device manufactured by themanufacturing method and the apparatus in accordance with one of theembodiments of the present invention is incorporated in a spindle motor.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings. FIG. 1 is aschematic view of an apparatus for wiping-off lubricating oil as a firstmanufacturing apparatus for carrying out a first method formanufacturing a hydro dynamic bearing device in accordance with thepresent invention. FIGS. 2A and 2B are diagrams for illustrating theinner structure of the hydro dynamic bearing device, FIG. 2A being avertical cross sectional view thereof, and FIG. 2B being an enlargedview of a part marked with the symbol A in FIG. 2A.

For the sake of convenience in description, the configuration of a hydrodynamic bearing device will be described at first in advance to thedescription of a wiping-off apparatus for carrying out the firstmanufacturing method.

As shown in FIG. 2A, the hydro dynamic bearing device 1 mainly includesa housing 7 in a bottomed cylindrical shape having an opening part 7 ain its one end, a cylindrical bearing sleeve 8 fixed on the innerperiphery of the housing 7, an axial member 2 arranged on the innerperiphery of the bearing sleeve 8, and a sealing member 10 fixed on theopening part 7 a of the housing 7.

The housing 7 is formed of a soft metallic material such as brass (ormay be formed of stainless steel, stainless steel pipe, resin material,or the like). The housing 7 includes a cylindrical lateral part 7 b anda bottom part 7 c. In addition, for example a spiral hydro dynamicpressure generating groove (not shown) may be formed on the region to beprovided as a thrust bearing surface of the inner bottom surface 7 c 1of the bottom part 7 c. In this embodiment, furthermore, the lateralpart 7 b and the bottom part 7 c of the housing 7 areseparately-prepared structural components being fixed to each other withappropriate connecting means. For example, a lid-shaped member to serveas the bottom part 7 c is caulked in and bonded to the other-end openingpart of the lateral part 7 b. Alternatively, the lateral part 7 b andthe bottom part 7 c may be provided as an integral structure.

The axial member 2 is formed of a metallic material such as stainlesssteel or aluminum. The axial member 2 includes an axial part 2 a and aflange part 2 b. The flange part 2 b is integrally or separately mountedon the lower end of the axial part 2 a. Furthermore, a hollow 2 a 1 anda tapered surface 2 a 2 are formed in the outer peripheral surface ofthe axial part 2 a. The tapered surface 2 a 2 has a predetermined taperangle to gradually decrease the diameter thereof from the lower end tothe upper end thereof (see FIG. 2B), while a cylindrical surface 2 a 3of the axial part 2 a is formed immediately above the tapered surface 2a 2 in a continuous manner.

The bearing member 8 is formed from a porous material or the like,particularly a sintered metal mainly comprising copper. Thus, pores areformed in the bearing member 8, so that these pores can be impregnatedwith lubricant oil to provide an oil-containing bearing. On the innerperipheral surface 8 a of the bearing member 8, upper and lower radialbearing surfaces R1 and R2 are formed. In addition, a spacing part R3 isinterposed between the surfaces R1 and R2 to separate these surfaces R1,R2 in the axial direction. Each of the bearing surfaces R1, R2 has ahydro dynamic pressure generating groove with the herringbone shape (notshown). Also, the spacing part R3 faces to the hollow 2 a 1 of the axialpart 2 a, and the clearance between the spacing part R3 and the hollow 2a 1 is set to be larger than the radial bearing clearance. The bottomsurface 8 c of the bearing member 8 has an area to be provided as athrust bearing surface. In such an area, a hydro dynamic pressuregenerating groove (not shown) in the shape of a spiral or the like isformed.

The sealing member 10 is formed like a ring and is fixed in the innerperipheral surface of the opening part 7 a of the housing 7 by means ofpress-fit and/or adhesive, or the like. In this embodiment, furthermore,the inner peripheral surface 10 a of the sealing member 10 is formedlike a cylinder and the lower end face 10 b of the sealing member 10abuts on the upper end face 8 b of the bearing member 8. The innerperipheral surface 10 a of the sealing member 10 faces to the taperedsurface 2 a 2 of the axial part 2 a through a predetermined clearancetherebetween. Between these components facing to each other, there isformed a sealing space S. This space S is provided as a tapered spacegradually expanded in the upward direction of the housing 7.

Next, a description is given of a first wiping-off apparatus (i.e., thefirst manufacturing apparatus) to be used in the first method formanufacturing a hydro dynamic bearing device having the inner structuredescribed above.

As shown in FIG. 1, the first wiping-off apparatus 20 includes a casingmember 21 in which an air-flowing space is formed, and a partitionmember 24 for dividing the air-flowing space into an air-blowing space22 located above and an air-vacuuming space 23 located below. Thepartition member 24 serves as a mounting member on which the hydrodynamic bearing device 1 is mounted. In this embodiment, the casingmember 21 includes an upper casing member 21 a and a lower casing member21 b which are fit together in a detachable manner such that themounting member (the partition member) 24 is integrally fixed on theupper end of the lower casing member 21 b to provide a combinedstructure.

The air-blowing space 22 is a space defined by the inner peripheralsurface 21 aa of the upper casing member 21 a, the ceiling surface 21 abof the upper casing member 21 a, and the upper surface 24 a of themounting member 24. The air-vacuuming space 23 is a space defined by theinner peripheral surface 21 ba of the lower casing member 21 b and thelower surface 24 b of the mounting member 24. An insert hole 24 c isformed in the central part of the mounting member 24. Therefore, anaxial part 2 a (the axial part 2 a protruded outward from the sealingmember 10 of the axial member 2) where the sealing member 10 directsdownward is inserted into the insert hole 24 c with play. In addition, aplurality of through-holes 25 is formed on the outer peripheral side ofthe mounting member 24. These holes 25 allow the air-blowing space 22 tocommunicate with the air-vacuuming space 23, respectively.

As shown in the figure, in a state of mounting the hydro dynamic bearingdevice 1 on the mounting member 24, the outer end face 10 x of thesealing member 10 is arranged in close contact with the upper surface 24a of the mounting member 24. In addition, an air-flowing clearance 26 isformed between the outer peripheral surface 7 x of the housing 7 and theinner peripheral surface 21 aa of the air-blowing space 22. Furthermore,a plurality of through-holes 25 is opened in the upper surface 24 a ofthe mounting member 24 so as to be substantially circumscribed on theouter peripheral side of the outer peripheral surface 7 x of the housing7.

On the upper end part of the casing member 21, a single air-dischargingnozzle 27 (air-blowing means) from which the air is dischargeddownwardly from a discharge port 27 a on the tip thereof to theair-blowing space 22 is installed. In addition, vacuum means (not shown)for sucking the air from the air-vacuuming space 23 is equipped on theside below the lower end part of the casing member 21. The airdischarged from the air-discharging nozzle 27 passes through theair-flowing passage 28 extending from the outer bottom surface 7 y tothe outer peripheral surface 7 x of the housing 7 of the hydro dynamicbearing device 1 and reaches the air-vacuuming space 23 through thethrough-holes 25, followed by being sucked downward by the vacuum means.In this embodiment, the outer end face 7 z of the housing 7 and theouter end face 10 z of the sealing member 10 are arranged in closecontact with the upper surface 24 a of the mounting member 24, so thatthe air cannot be introduced into the close-contacting region.

The first apparatus for wiping off the lubricating oil, which isconfigured as described above, is used as follows in the process ofmanufacturing the hydro dynamic bearing device 1.

That is, for lubricating the hydro dynamic bearing device 1 in whicheach structural component has been assembled in the state as shown inFIG. 2, the hydro dynamic bearing device 1 is assembled at first withoutlubrication and then the hydro dynamic bearing device 1 is dipped intothe lubricating oil in a vacuum tank. Consequently, the air in the innerspace of the housing 7 is sucked under vacuum in the vacuum tank andthen exhausted. As a result, the inner space of the housing 7 is in astate of being evacuated. After that, the inner space of the housing 7is opened to the atmospheric pressure to fill the inner space of thehousing 7 with the lubricating oil.

When the lubrication is completed as described above, the hydro dynamicbearing device 1 is pulled out of the vacuum tank. In the removed hydrodynamic bearing device 1, a large amount of the lubricating oil adheresto the outer bottom surface 7 y and the outer peripheral surface 7 x ofthe housing 7, the outer end face 10 z of the sealing member 10, and theouter end face 2 z and the outer peripheral surface 2 y of the axialpart 2 a protruded outwardly from the sealing member 10.

In the subsequent wiping-off step, the hydro dynamic bearing device 1 isplaced on the mounting member 24 of the wiping-off apparatus 20 as shownin FIG. 1, and then the high-pressure air is discharged downwardly fromthe air-discharging nozzle 27. Consequently, the air flow along theouter bottom surface 7 y and the outer peripheral surface 7 x of thehousing 7 is generated.

Specifically, the high-pressure air in the air-blowing space 22 comesinto collision with the outer bottom surface 7 y of the housing 7 asindicated by the arrow a in FIG. 1 to blow off the lubricating oiladhering to the outer bottom surface 7 y, while flowing along the outerperipheral surface 7 x of the housing 7 to stream the lubricating oiladhering to the outer peripheral surface 7 x with blowing. Consequently,the air passes through the through-holes 25 of the mounting member 24together with mist of the lubricating oil, reaching the air-vacuumingspace 23.

The air including the mist of the lubricating oil reaching theair-vacuuming space 23 is sucked downward by the vacuum means as shownin the arrow b in the figure. Therefore, the air maintains its high flowrate by the synergistic action between the downward discharge pressurecaused by the air-discharging nozzle 27 and the downward suction forcecaused by the vacuum means, while flowing along the outer bottom surface7 y and the outer peripheral surface 7 x of the housing 7. Consequently,the lubricating oil adhering to these surfaces 7 x, 7 y can be wiped offby the air very aggressively.

In this case, as shown in FIG. 2, stepped parts 7 x 1, 7 x 2 are formedon the outer peripheral surface 7 x of the housing 7, and anotherstepped part 7 y 1 is also formed on the outer bottom surface 7 y of thehousing 7. However, the lubricating oil adhering to these stepped parts7 x 1, 7 x 2, and 7 y 1, which tends to be remained thereon, is alsowiped off by the air flow properly.

Referring now to FIG. 3, there is illustrated a second wiping-offapparatus (i.e., a second manufacturing apparatus) to be used in asecond method for manufacturing a hydro dynamic bearing device 1. Inother words, the second wiping-off apparatus is used in the subsequentstage of the wiping-off treatment or the prior stage of the treatment tothe outer bottom surface 7 y and outer peripheral surface 7 x of thehousing 7 by the first manufacturing apparatus 20 described above.

The second wiping-off apparatus 30 has a rotation jig 31 for supportingthe hydro dynamic bearing device 1 from beneath, while the outer endface 10 z (the outer end face 2 z of the axial part 2 a) of the sealingmember 10 is directed upward. The rotation jig 31 is constructed so asto rotate about the axial center Z in the direction indicated by thearrow r by the action of a stepping motor or a servo motor (not shown),thereby rotate the hydro dynamic bearing device 1 around the axialcenter Z. A recessed part 31 a formed in the rotation jig 31, in whichthe lower part of the hydro dynamic bearing device 1 is fit, preventsthe inclination of the hydro dynamic bearing device 1 at the time of therotation.

There are two suction nozzles 32 arranged above the rotation jig 3.These suction nozzles 32 are provided as suction means to makenegative-pressure suction forces act on the outer end face 2 z of theaxial part 2 a of the hydro dynamic bearing device 1 in a state of beingsupported on the rotation jig 31 and the outer end face 10 z, 7 z whichis the portion extending from the sealing member 10 to the housing 7.Each of the two suction nozzles 32, 32 are arranged so as to be inclinedat a predetermined angle of 30° to 65° with respect to a horizontalplane while each of their nozzle tips 32 a, 32 a is made abut on orsubstantially abut on each of the corresponding outer end faces 2 z, 10z (7 z), preferably via a clearance (e.g., 0.5 mm) between the nozzleand the outer end face 2 z, 10 z (7 z). In addition, the suction nozzles32 are constructed so as to move in the radial direction (e.g., areciprocate motion) by the action of nozzle-position control means 33.On the second wiping-off apparatus 30, there is arranged suction controlmeans 34 that controls a negative-pressure suction force generated byeach of the two suction nozzles 32. In other words, the suction controlmeans 34 controls the magnitude of the negative-pressure suction forceto act on each of the outer end faces 2 z, 10 z (7 z) described aboveand the generation and termination of negative pressure, and so on.

The second apparatus for wiping off the lubricating oil constructed asdescribed above is used in the process of manufacturing the hydrodynamic bearing device 1 as follows.

That is, the hydro dynamic bearing device 1 having been lubricated withthe lubricating oil described above is placed on the rotation jig 31 asshown in FIG. 3 before or after wiping off the lubricating oil on theouter bottom surface 7 y and the outer peripheral surface 7 x of thehousing 7, followed by rotating the rotation jig 31. Thereby, the hydrodynamic bearing device 1 is rotated about the axial center z in thedirection of the arrow r.

Under these circumstances, the nozzle tips 32 a, 32 a of the two suctionnozzles 32, 32 are displaced to positions where they are brought into astate of having respective clearances between the nozzle tip 32 a andthe outer end face 2 z of the axial member 2 a and between the nozzletip 32 a and the outer end faces 10 z, 7 z of the sealing member 10 andhousing 7. Furthermore, if required, the nozzle tips 32 a, 32 a of thetwo suction nozzles 32, 32 are reciprocated in the radial direction. Atthe same time, the activation of the suction control means 34 generatesnegative-pressure suction forces in two suction nozzles 32 to suck anexcess amount of the lubricating oil adhering to each of the outer endfaces 2 z, 10 z, 7 z.

Consequently, an excess amount of the lubrication oil can be wiped offfrom each of the whole area of the outer end face 2 z of the axial part2, the whole area of the outer end face 10 z of the sealing member 10,and the whole area of the outer end face 7 z of the housing 7. In thiscase, as shown in FIG. 2, a recessed part 17 is formed between the outerend face 7 z of the housing 7 and the outer end face 10 z of the sealingmember 10. Even though the lubricating oil adheres to the recessed part17 and tends to be remained therein, it can be properly wiped off by thenegative-pressure suction force of the suction nozzle 32. Furthermore,the lubricating oil can be sufficiently sucked by the negative pressureeven though the suction nozzle 32 is held in its fixed position withoutallowing a reciprocating motion in the radial direction because each ofthe outer end face 2 z of the axial part 2 a and the outer end faces 10z, 7 z extending from the sealing member 10 to the housing 7 has anextremely small area.

In FIG. 4, just as with the above description, there is shown anotherexample of the second wiping-off apparatus (another example of thesecond manufacturing apparatus) for wiping off the lubricating oiladhering to the outer end face 2 z of the axial part 2 a and the outerend faces 10 z, 7 z extending from the sealing member 10 to the housing7.

The wiping-off apparatus 40 includes: a motor 41 fixed on a base F suchthat a rotary shaft 41 a is in an upright state and is directed upward;a receiving member 42 fixed on the upper end part of the rotary shaft 41a of the motor 41 such that it rotates together with the rotary shaft 41a; and a rotation jig 44 attached above the receiving member 42 througha bearing 43 (e.g., an angular bearing). Furthermore, the lower part ofthe hydro dynamic bearing device 1 in which the outer end face 10 z ofthe sealing member 10 is directed upward is fixed and held in therecessed part 44 a formed on the upper face part of the rotation jig 44.

In addition, a vertical elevating mechanism 46 is arranged above therotation jig 44. The vertical elevation mechanism 46 is responsible formaking the oil-absorbing member 45 abut to or move away from the outerend faces 10 z, 7 z of the sealing member 10 and the housing 7 of thehydro dynamic bearing device 1 by vertically moving the oil-absorbingmember 45 such as a cotton swab. The vertical elevating mechanism 46includes a weight 48 fixed on the upper part of the oil-absorbing member45 through a connecting rod 47, an oscillating member 50 supported on anintermediate shaft 49 so as to be able to oscillate about theintermediate shaft 49 to vertically move the oil-absorbing member 45together with a weight 48, and an eccentric cam 53 for oscillating theoscillating member 50 by cooperating with a spring force of a spring 52.In this case, one end part of the oscillating member 50 is placedbetween upper and lower collar parts 54, 54 fixed on the middle part inthe vertical direction of the connecting rod 47 such that it movestogether with the up and down movements of the connecting rod 47. Inaddition, the other end part of the oscillating member 50 is constructedsuch that it is constantly kept in contact with the outer peripheralsurface of the eccentric cam 53 by a spring force of the spring 52.

The wiping-off apparatus 40 described above wipes off the lubricatingoil on the basis of the following action.

That is, the rotary shaft 41 a of the motor 41 is constantly rotated.Under such a condition, the eccentric cam 53 and the oscillating member50 push up the oil-absorbing member 45 together with the weight 48.During this movement, the oil-absorbing member 45 is moved away from thehydro dynamic bearing device 1, so that the rotation jig 44 and thehydro dynamic bearing device 1 can rotate about the axial center Z asthe receiving member 42 rotates.

In contrast, the eccentric cam 53 and the oscillating member 50 pushdown the oil-absorbing member 45 together with the weight 48. When theoil-absorbing member 45 abuts against the outer end face 10 z of thesealing member 10 and the outer end face 7 z of the housing 7, thebearing 43 runs idle by the force caused by the abutment. Accompaniedwith such a movement, the rotary motions of the rotation jig 44 and thehydro dynamic bearing device 1 are stopped. At the time of stopping therotation, the lubricating oil is wiped off from each of the outer endfaces 10 z, 7 z by the oil-absorbing member 45.

After that, the movements of eccentric cam 53 and oscillating member 50push up the oil-absorbing member 45 again together with the weight 48.In addition, each of the rotation jig 44 and the hydro dynamic bearingdevice 1 is rotated by a predetermined angle, followed by pushing downthe oil-absorbing member 45 together with the weight 48. Consequently,the oil-absorbing member 45 abuts on the outer end faces 10 z, 7 z ofthe sealing member 10 and the housing 7 of the hydro dynamic bearingdevice 1 to stop the rotation of the hydro dynamic bearing device 1 towipe off the lubricating oil from each of the outer end faces 10 z, 7 z.

Consequently, the hydro dynamic bearing device 1 intermittently rotatesabout the axial center Z and the lubrication oil is wiped off by theoil-absorbing member 45 only at the time of stopping the rotation.Therefore, there is no sliding movement occurring between the outer endface 10 z of the sealing member 10 and the oil-absorbing member 45, sothat an oil-repellent agent applied to the inner periphery side of thesealing member 10 is effectively protected from being removed withfriction or the like while the lubricating oil can be efficiently wipedoff.

Furthermore, in the step previous to the step of lubrication describedabove and also previous to assemble the hydro dynamic bearing device 1,an ion-removing washing with ultra pure water is performed on each ofthe structural components of the hydro dynamic bearing device 1. In thiscase, it is preferable to control the removing speed of pulling eachstructural component (hereinafter, also referred as a product to bewashed) out of the water to the air. Specifically, the removing speed isdefined in the range of 20 mm/s or less, preferably in the range of 10to 20 mm/s. When the removing speed is 20 mm/s or less, the amount ofions attached on the product to be washed (i.e., the attached amount ofwater in which ionic ingredients are dissolved) decreases in apreferable manner. When the removing speed is over than 20 mm/s, ourexperiments revealed that the attached amount of ions on the product tobe washed increased in an undesirable manner. When the removing speed is10 mm/s or less, there is a trouble in which the attached amount of ionsdoes not decrease and the time required for pulling the product to bewashed becomes prolonged too much.

In the ion-removing washing with ultra pure water, after pulling theproduct to be washed out of water to the air, before transferring to asubsequent washing bath or a next step (drying step), it is preferableto shake off the attached water by applying oscillation or impact(shock) to the product to be washed.

Furthermore, when the ion-removing washing with ultra pure water isperformed, it is preferable to control the amount of water attached onthe product to be washed and the temperature of the product to be washedat the time of conducting the step of drying the water being attached onthe product to be washed under vacuum. Specifically, it is preferable tocontrol the amount of water attached on the product to be washed (M) andthe temperature of the product to be washed (T₁) before drying so as tosatisfy the following equation and inequality:

n×m×Δ=MQ

T ₁ −ΔT>0

where the specific heat of the product to be washed is n(cal/(g·° C.)),the weight of the product to be washed is m(g), the change intemperature is ΔT(° C.), the amount of water being attached is M(g), andthe evaporation heat of water is Q(cal/g)·583 (cal/g). Furthermore,preferably, the above product to be washed may be made of copper alloyand also it may be a structural component of the hydro dynamic bearingdevice for use in an HDD spindle motor.

Consequently, an efficiency of the washing can be increased bycontrolling the rate of pulling the product to be washed so as to attaina decrease in the amount of water being attached on the product to bewashed. In addition, the drying time can be shortened by controlling thetemperature of the product to be washed at the time of vacuum drying. Asa result, an advantage of improving the working efficiency can beattained.

FIG. 5 is a schematic diagram for illustrating an oil level controller(a third manufacturing apparatus) to be used in a third method formanufacturing a hydro dynamic bearing device as an embodiment of thepresent invention. The third manufacturing device 60, i.e., themanufacturing apparatus 60 used for adjusting the amount of oil in thehydro dynamic bearing device 1, includes: a rotation jig 61 thatsupports the bottom part of the lubricated hydro dynamic bearing device1 from beneath and is capable of rotating about the axial center (in thedirection indicated by the arrow R or the opposite direction as shown inFIG. 5); and an elevating jig 62 arranged on the upper side of the hydrodynamic bearing device 1 and capable of moving up and down. In thiscase, the elevating jig 62 may be kept in place while the rotation jig61 may be capable of moving up and down.

The elevating jig 62 is capable of moving close to and moving away fromthe upper end face of the housing 7 (the upper surface of the sealingmember 10 described below) of the hydro dynamic bearing device 1. Inaddition, on the elevating jig 62, there is provided a suction nozzle 63as suction means where the axial center thereof is inclined at an angle□ of 45° to 65° (preferably, at an angle of 55°) with respect to thehorizontal plane. Furthermore, the nozzle tip 63 a of the suction nozzle63 is located between the axial member 2 and the sealing member 10 tocontrol the magnitude and the generation time period of thenegative-pressure suction force generated in the suction nozzle 63 bythe action of suction control means 64.

FIGS. 6A and 6B are a view showing the inner structure of the hydrodynamic bearing device 1 and a view showing the state of arranging thesuction nozzle 63 with respect to the internal structure of the hydrodynamic bearing device 1, respectively. The details of the hydro dynamicbearing device 1 are similar to those shown in FIGS. 2A and 2Breferenced in the first and second manufacturing methods describedabove. Therefore, the explanations of common structural components willbe omitted while denoted by the same reference numerals.

In this embodiment, when applying the lubricating oil to the housing 7of the hydro dynamic bearing device 1, just as with the case describedabove, the hydro dynamic bearing device 1 is assembled at first withoutlubrication and then the hydro dynamic bearing device 1 is dipped intothe lubricating oil in a vacuum tank, followed by releasing to theatmospheric pressure to fill the inner space of the housing 7 with thelubricating oil.

When the lubrication is completed as described above, the hydro dynamicbearing device 1 is pulled out of the vacuum tank. Then, the wiping-offstep according to the first and second manufacturing methods describedabove is conducted properly if required. Subsequently, as shown in FIG.5, the hydro dynamic bearing device 1 is heated up to an upper limittemperature of the operation in a state where the lower part of thehousing 7 is held with the rotation jig 61, or the hydro dynamic bearingdevice 1 is heated up to an upper limit temperature of the operation andis then held with the rotation jig 61.

With this heating, the thermal expansion of lubricating oil filled inthe inner space of the housing 7 increase the oil-level L of thelubricating oil, for example as shown in FIG. 6B. At this time, theelevating jig 62 is located at the lower moving end or thereabout, or ina state of being moved down. That is, the nozzle tip 63 a of the suctionnozzle 63 is located between the sealing member 10 and the axial member2, more specifically located near the upper end of the sealing space S.If required, the positional control is performed by moving the suctionnozzle 63 from the state shown in the figure downward by the action ofthe suction control means 64 or the action of means for driving theelevation of the elevating jig 62. In addition, it may be constructedsuch that the suction nozzle 63 can be precisely positioned at the timewhen the lower end face of the elevating jig 62 is made abut on theupper end face of the sealing member 10. Furthermore, in a state wherethe position of the nozzle tip 63 a is being set to a previously definedheight, the rotation jig 61 is rotated in the direction indicated by thearrow R, thereby rotate the hydro dynamic bearing device 1 about theaxial center Z (see FIG. 5).

In the same time period, the action of the suction control means 64allows the nozzle tip 63 a of the suction nozzle 63 to suck thelubricating oil for a predetermined time under a predetermined pressure.Therefore, an excess amount of the lubricating oil is exhausted outsidethrough the suction nozzle 63 at the upper limit temperature of theoperation, resulting in an appropriate oil-level height in the sealingspace S. Subsequently, the heating is terminated and the temperature ofthe hydro dynamic bearing device 1 is then returned to a roomtemperature. Then, the oil-level height of the lubricating oil in thesealing space S decreases a predetermined level as the temperaturedecreases and finally settles down to an ideal height, oil-level L1,shown in FIG. 6B.

When the suction force (negative pressure value), suction time, and theposition of the nozzle tip 63 a of the suction nozzle 63 are properlychanged, an excess amount of the lubricating oil can be sucked from thesealing space S at room temperature to keep the oil-level L1 at an idealheight, oil-level L1, without heating the hydro dynamic bearing device 1as described above. In addition, at the time of sucking the lubricatingoil with the suction nozzle 63, there is no need to rotate the hydrodynamic bearing device 1. Therefore, for the hydro dynamic bearingdevice 1 being fixed and held in the fixed position, an excess amount ofthe lubricating oil may be sucked with the suction nozzle 63 just aswith the above description from one part of the sealing space S.

After that, the oil-level height is detected using a laser displacementmeter. However, as shown in FIG. 7, the oil-level L1 is shaped like aconcave-curved surface, so that the position of irradiating the laser issifted in the radial direction as indicated by the arrows in the figure,the height of the oil-level L1 to be detected is also differed.Therefore, when the axial member 2 is eccentric or the like, the laseris hardly irradiated on the position of the oil-level L1 to be detected.Thus, in this embodiment, it is constructed such that the position of alaser irradiation part is finely adjusted using a micrometer head.Consequently, by precisely detecting the height of the oil-level L1, itbecomes possible to select the good product and the defective productwith respect to the hydro dynamic bearing device 1 with high accuracy.

FIG. 8 shows an oil-level height detector 65 for detecting an oil-levelheight of lubricating oil filled in the housing 7 using laser beams. Asshown in the figure, the oil-level height detector 65 includes a laserdisplacement meter 66 as laser displacement determining means. The laserdisplacement meter 66 is arranged above the hydro dynamic bearing device1 at a position a predetermined distance away from the upper end surfaceof the sealing member 10 (the upper end surface of the housing 7). Thelaser displacement meter 66 can vertically emit laser beams downward (ina direction parallel to the axial center Z). In this embodiment, thesingle laser displacement meter 66 is attached to the lower surface of asliding table (X table) 67 composed of an X table which can move onlyalong one straight line within a horizontal plane (a plane to which theaxial center Z is perpendicular).

The oil-level height of the lubricating oil can be determined by theoil-level height detector 65 in the following manner. First, the laserdisplacement meter 66 at a first measuring position illustrated in solidline irradiates the oil surface L1 of the lubricating oil with laserbeams. At this time, a time period from emission of laser beams toreceiving of laser beams reflected by the oil surface L1 is determinedand converted into a distance T1 from the standard position 66 a of thelaser displacement meter 66 (laser irradiation part) to the oil surfaceL1. Next, the laser displacement meter 66 is moved by the sliding table67 horizontally, thereby positioning the meter 66 at the next nearestposition illustrated in broken line. Then, the laser displacement meter66 irradiates the upper end surface of the sealing member 10 with laserbeams. At this time, a time period from emission of laser beams toreceiving of laser beams reflected by the upper end surface of thesealing member 10 is determined and converted into a distance T2 fromthe standard position 66 a of the laser displacement meter 66 to theupper end surface of the sealing member 10. Then, based on thedifference between the two distances T1 and T2, an oil-level height(T1-T2) of the lubricating oil at the first position can be determined.

The laser displacement meter 66 is moved to a second measuring positionseparated by 180 degrees from the first position by the sliding table67. The same determining process is carried out there to determine anoil-level height (T3-T4) of the lubricating oil at the second position.Then, an average of the oil-level height (T1-T2) at the first positionand the oil-level height (T3-T4) at the second position is assigned toan oil-level height Tx of the hydro dynamic bearing device 1 (anoil-level height on the basis of the upper end surface of the sealingmember 10). Based on the oil-level height Tx, whether the amount of thelubricating oil filled in the housing 7 is proper or not is judged tojudge whether the hydro dynamic bearing device 1 of interest is a goodproduct or not. If it is judged as a defective product, lubricatingprocess or oil amount adjustment process is performed again, before theoil-level height Tx is determined again using the laser displacementmeter 66 in the same manner as described above.

By determining an oil-level height in the hydro dynamic bearing device 1using the laser displacement meter 66, it is possible to confirm whetherthe oil amount is proper or not with accuracy. This helps the properhydro dynamic pressure action and lubrication action of the hydrodynamic bearing device 1 while drastically decreasing the possibility ofoccurrence of lubricating oil leakage during the operation of the hydrodynamic bearing device 1. In this embodiment, the oil-level heightdetector 65 can detect an oil-level height using a single laserdisplacement meter 66. However, a plurality of laser displacement meters66 can be used for oil-level detection. In this embodiment, theoil-level height is determined at two circumferential positions aroundthe axial center Z. Instead, the oil-level height may be determined atone position or three or more positions. In this embodiment, theoil-level height detection using laser beams is performed afteradjusting the amount of lubricating oil in the housing 7 by sucking theoil under a negative pressure as described above. However, the oiladjusting methods other than this may be adopted, such as sucking oilwithout using a negative pressure and wiping off oil.

After performing each of the above steps, the finishing treatmentincluding a subsequent step of removing the adhering oil (e.g., awiping-off treatment using the apparatus shown in FIG. 4 and describedabove) is performed to provide a completed product of the hydro dynamicbearing device 1. The hydro dynamic bearing device 1 obtained as acompleted product is used as one of structural components of a motor asdescribed below.

That is, a spindle motor 70 for an information technology device asillustrated in FIG. 9 is used in a disk driving device such as a harddisk drive (HDD). The spindle motor 70 includes a disk hub 71 mounted onthe axial member 2 of the above hydro dynamic bearing device 1, and amotor stator 72 and a motor rotor 73 facing to each other through aclearance in the radial direction or the like. The stator 72 isinstalled on the outer periphery of a casing 74 and the rotor 73 isinstalled on the inner periphery of the disk hub 71. The housing 7 ofthe hydro dynamic bearing device 1 is attached on the inner periphery ofthe casing 74. In the disk hub 71, one or more magnetic disks or thelike are held. Then, by energizing the stator 72, an excitation forcegenerated between the stator 72 and the rotor 73 rotates the rotor 73,thereby rotating the disk hub 71 and the axial member 2 together.

Then, accompanying the rotation of the disk hub 71, even though thetemperature of the hydro dynamic bearing device 1 increases to atemperature near the upper limit temperature of the operation, theleakage of the lubricating oil filled in the housing 7 from the sealingspace S to the outside can be properly avoided. Therefore, it becomespossible to effectively prevent the functional defective of the motor 70caused by the leakage of the lubricating oil and also effectivelyprevent the disk D from being suffered from undesired influencesthereof, and so on.

In all of the embodiments described above, the present invention isapplied to the hydro dynamic bearing device of the type that the sealingspace is formed between the sealing member and the axial member.However, the present invention is not limited thereto, and just as withthe above embodiments, the present invention may be applied to a hydrodynamic bearing device of the type that the sealing member is formed soas to cover the region extending from the whole area on the upper endside of the housing to the outer peripheral side of the upper end partin a state where the sealing member is integrally fixed on the axialmember, and the sealing space is formed between the outer peripheralsurface of the upper end part of the housing and the inner peripheralsurface of the sealing member, which are faced to each other.

In addition, in all of the embodiments described above, the presentinvention is applied to the hydro dynamic bearing device where the axialmember having the flange part is used and the hydro dynamic pressuregenerating groove of the thrust bearing part is formed on both end facesof the flange part or the surfaces facing to these end faces. However,the present invention is not limited thereto, and just as with the aboveembodiments, the present invention may also be applied to a hydrodynamic bearing device which is constructed such that an axial memberhaving no flange part is used and the end face of the axial member isheld by the thrust plate attached on the bottom surface of the housingwithout forming the hydro dynamic pressure generating groove in thebearing surface as a thrust bearing part.

Furthermore, in all of the above embodiments, the present invention isapplied to the hydro dynamic bearing device constructed of the housingand the sealing member which are separately mounted. However, thepresent invention is not limited thereto, and just as with the aboveembodiments, the present invention may also be applied to a hydrodynamic bearing drive constructed of the housing and the sealing member(the sealing part) which are integrally formed together.

Furthermore, in all of the above embodiments, the present invention isapplied to the hydro dynamic bearing device constructed of the housing,the bearing member, and the sealing member which are separately mounted.However, the present invention is not limited thereto, and just as withthe above embodiments, the present invention may also be applied to ahydro dynamic bearing drive constructed of the three structuralcomponents which are integrally formed together.

As described above, according to the method and the apparatus formanufacturing the hydro dynamic bearing device of the present invention,the lubricating oil adhering at least to the outer bottom surface andthe outer peripheral surface of the housing is blown off or streamedwith blowing by blowing the gas on these surfaces at the time of wipingoff the lubricating oil adhering to the device in a subsequent stepafter applying the lubricating oil to the unlubricated hydro dynamicbearing device. Therefore, there is no need of conducting any difficultor complicated work required for the wiping off with a resin film, whichhas been required in the conventional method. Therefore, it becomespossible to improve the working efficiency to a large extent. Inaddition, even though a recessed part or a stepped part is formed in thehousing, the lubricating oil that tends to be remained in the recessedor stepped part can easily be wiped off by the gas, so that it becomespossible to obtain a high-quality hydro dynamic bearing device.

In this case, a gas-flowing passage may be formed such that a gas fromthe single gas-blowing means flows along the outer bottom surface andthe outer peripheral surface of the housing. Consequently, only byproviding the single gas-blowing means, the lubricating oil adhering toboth the above surfaces of the housing can be wiped off all at once bythe gas. Therefore, the configuration of the apparatus described abovecan reduce the number of structural parts of the device to be used forthe wiping-off operation, can achieve the miniaturization of the device,and also reduce the cost of the device, while contributing a reductionin the manufacturing costs.

Furthermore, the area extending from the outer end face of the sealingpart to the axial member is shielded from the gas-flowing passage whenthe hydro dynamic bearing device is held such that the sealing part islocated below. Therefore, even though the lubricating oil flows downwardon the gas-flowing passage along the housing, there is no possibility ofcausing trouble in which the lubricating oil flows and adheres to theouter end face of the sealing part or to the axial member, or thelubricating oil flows into a sealing space between the sealing part andthe axial member.

According to the method and the apparatus for manufacturing the hydrodynamic bearing device, the lubricating oil adhering at least to theouter end face of the sealing part and the outer end face of the axialmember is wiped off by sucking the oil with the action of thenegative-pressure suction force caused by the suction means at the timeof wiping off the lubricating oil adhering to the hydro dynamic bearingdevice in a subsequent step of applying the lubricating oil to theunlubricated hydro dynamic bearing device. There is no need of difficultand complicated work of wiping off the lubricating oil using a resinfilm or the like. Thus, it becomes possible to improve the workingefficiency to a large extent. In addition, even though the axial memberprotrudes from the sealing part outside, the procedure based onnegative-pressure suction substantially prevent the axial member fromstanding in the way of wiping off the lubricating oil. Therefore, thewiping can be performed appropriately without improperly remaining theundesired lubricating oil on a part where it is difficult to wipe thelubricating oil due to the presence of the axial member.

In this case, when the suction means is constructed of two suctionnozzles respectively corresponding to the outer end face of the sealingpart and the outer end face of the axial member, the amount of thelubricating oil being sucked can be stably adjusted and also easilymanaged by managing the nozzle diameter, nozzle-tip position, andsucking force of each suction nozzle. Furthermore, the nozzle tip can beeasily close to a part where it is difficult to wipe off the lubricatingoil due to the presence of the axial member. Therefore, the wiping-offoperation can be more appropriately performed.

Furthermore, when the lubricating oil is sucked and wiped off by thesuction means while rotating the hydro dynamic bearing device about theaxial center, the suction means is only held on a fixed position or asimple reciprocating-motion such as a swing motion of the suction meansis only required. This contributes a simplification of the mechanism formoving the suction means and also contributes a simplification of thedevice required for the wiping-off operation and a cost reduction inproviding such a device.

In addition, according to the method and the apparatus for manufacturingthe hydro dynamic bearing device, the lubricating oil is sucked from thesealing space of the sealing part or the vicinity thereof using thesuction means that generates a negative-pressure suction force at thetime of adjusting the amount of oil in the housing after applying thelubricating oil to the unlubricated hydro dynamic bearing device.Therefore, the control of the suction force and also the control of thesuction oil amount can be performed stably, compared with theconventional method that uses a naturally-absorbing action with a cottonswab or the like. Consequently, it becomes possible to easily controlthe oil-level height and the amount of the oil in the housing withoutvariation, so that problems of early deterioration of the bearing devicedue to a leakage of the lubricating oil to the outside and poorlubrication at the time of driving the hydro dynamic bearing device atan upper limit temperature of the operation can be effectively avoided.

Furthermore, at the time of adjusting the amount of oil, the oil-levelheight may be measured by a laser after sucking the lubricating oil.Consequently, a high-quality hydro dynamic bearing device can beprovided in the market since the selection between the good product andthe defective product can be performed by confirming whether the suctionoil amount of the lubricating oil by the suction means is correct usinga laser.

Furthermore, according to the method and the apparatus for manufacturingthe hydro dynamic bearing device of the present invention, there isprovided the suction means that adjusts the oil-level height of thelubricating oil in the housing by sucking the lubricating oil from thesealing space of the sealing part or the vicinity thereof under anegative pressure. Therefore, it becomes possible to precisely andeasily manage the oil-level height and the amount of the lubricatingoil. Problems of early deterioration of the bearing device due to aleakage of the lubricating oil to the outside and poor lubrication atthe time of driving the hydro dynamic bearing device at an upper limittemperature of the operation can be effectively avoided.

Furthermore, since the suction means includes a suction nozzle, thenozzle diameter, nozzle-tip position, suction force, and suction time ofthe suction nozzle can be managed to adjust the oil-level height in astable manner and to manage such an adjustment in a simple manner.Therefore, Problems of early deterioration of the bearing device due toa leakage of the lubricating oil to the outside and poor lubrication atthe time of driving the hydro dynamic bearing device at an upper limittemperature of the operation can be avoided more effectively.

Furthermore, the suction means is capable of being close to or beingaway from the sealing space in a relative manner. Consequently, itbecomes possible to place the suction means on the sealing space or thevicinity thereof when the amount of lubricating oil in the housingshould be adjusted. Also it is possible to relatively displace thesuction means away from the sealing space when the adjustment of theamount of oil is not performed. Thus, for example, it becomes possibleto make the fabrication procedure automatic and also to speedup theprocedure when the hydro dynamic bearing device is produced on anassembly line.

Furthermore, the rotation jig for rotating the hydro dynamic bearingdevice about an axial center is equipped in the apparatus. According tosuch a configuration of the apparatus, it becomes possible to suck thelubricating oil by the suction means while rotating the hydro dynamicbearing device about the axial center by the rotation jig. As thesuction means is allowed to suck the lubricating oil directly over theentire perimeter of the sealing space, the amount of the lubricating oilcan be adjusted more precisely and uniformly.

In addition, a laser for measuring the oil-level height of thelubricating oil after sucking the oil is provided. In this case, ahigh-quality hydro dynamic bearing device can be provided in the marketsince the selection between the good product and the defective productcan be performed by confirming whether the suction oil amount of thelubricating oil by the suction means is correct using a laser.

Furthermore, according to the method and apparatus for manufacturing thehydro dynamic bearing device of the present invention, the oil-levelheight of the lubricating oil in the housing can be detected by a laser(laser displacement determining means). Consequently, after lubricatingthe hydro dynamic bearing device during the manufacturing process,whether the oil amount filled in the housing is proper or not can beconfirmed by means of a laser (laser beam). It is possible to detectwhether the oil amount is insufficient or excess with accuracy incomparison with the prior art. Further, it contributes to automation ofthe oil-level height detection.

1-17. (canceled)
 18. An apparatus for manufacturing a hydro dynamicbearing device including a housing, an axial member housed in thehousing, a radial bearing part for supporting the axial member in anon-contact manner in a radial direction by a hydro dynamic pressureaction of a lubricating oil generated in a radial bearing clearance, anda sealing part formed on one end part of the housing, the apparatuscomprising a laser for measuring an oil-level height of the lubricatingoil in the housing.